What steps can be taken to troubleshoot a "Call to undefined function" error in PHP?

The "Call to undefined function" error in PHP typically occurs when a function is called that has not been defined or included in the current script. To troubleshoot this error, you should first check if the function is defined in the same script or included from an external file. If the function is defined in an external file, make sure to include or require that file before calling the function.

// Example of including a file that defines the missing function
require_once 'functions.php';

// Call the function that was previously undefined
myUndefinedFunction();